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Basic Instinct A number of modern theorists
carry on Darwin’s tradition in their emphasis on a set of basic, innate
emotions. For many, basic emotions are defined by universal facial expressions
that are similar across many different cultures. In Darwin’s day,
the universality of emotional expression across cultures was presumed from
casual observation, but modern researchers have gone into remote areas of
the world to firmly establish with scientific methods that at least some
emotions have fairly universal modes of expression, especially in the face.
On the basis of this kind of evidence, the late Sylvan Tomkins proposed
the existence of eight basic emotions: surprise, interest, joy, rage, fear,
disgust, shame, and anguish These were said to represent innate, patterned
responses that are controlled by ‘hardwired’ brain systems.
A similar theory involving eight basic emotions has been proposed by Carrol
Izard Paul Ekman has a shorter list, consisting of six basic emotions with
universal facial expression: surprise, happiness, anger, fear, disgust and
sadness. Other theorists, like Robert Plutchick and Niko Frijda do not rely
exclusively on facial expressions, but instead argue for the primacy of
more global action tendencies involving many body parts. Plutchick points
out that as one goes down the evolutionary scale there are fewer and fewer
facial expressions, but still lots of emotional expressions involving other
bodily systems. Plutchik’s emotion list overlaps with the others,
but also diverges to some extent – it is similar to Ekman’s,
with the addition of acceptance, anticipation, and surprise. Phillip Johnson-Laird
and Keith Oatley approach the problem of basic emotions by looking at the
kinds of words we have for talking about emotions. They come up with a list
of five that overlaps with Ekman’s six, dropping surprise. Jaak Pankseep
has taken a different approach, using the behavioral consequences of electrical
stimulation of areas of the rat brain to reveal four basic emotional response
patterns: panic, rage, expectancy, and fear Other theorists have other ways
of identifying basic emotions and their lists also overlap and diverge from
the ones already described Most basic emotions theorists assume that there
are also non-basic emotions that are the result of blends or mixes of the
more basic ones. Izard, for example, describes anxiety as the combination
of fear and two additional emotions, which can be either guilt, interest,
shame, anger or distress. Plutchik has one of the better developed theories
of emotion mixes. He has a circle of emotions, analogous to a circle of
colors in which mixing of elementary colors gives new ones. Each basic emotion
occupies a position on the circle. Blends of two basic emotions are called
dyads. Blends involving adjacent emotions in the circle are first-order
dyads, blends involving emotions that are separated by one other emotion
are second-order dyads, and so on. Love, in this scheme, is a first-order
dyad resulting from the blending of adjacent basic emotions joy and acceptance,
whereas guilt is a second-order dyad involving joy and fear, which are separated
by acceptance. The further away two basic emotions are, the less likely
they are to mix. And if two distant emotions mix, conflict is likely. Fear
and surprise are adjacent and readily blend to give rise to alarm, but joy
and fear are separated by acceptance and their fusion is imperfect –
the conflict that results is the source of the emotion guilt.
The mixing of basic emotions into higher-order emotions is typically
thought of as a cognitive operation. According to basic emotions theorists,
some if not all of the biologically basic emotions are shared with lower
animals, but the derived or non-basic emotions tend to be more uniquely
human. Since the derived emotions are constructed by cognitive operations,
they could only be the same to the extent that two animals share the same
cognitive capacities. And since it is in the area of cognition that humans
are believed to differ most significantly from other mammals, non-basic,
cognitively-constructed emotions are more likely than basic emotions to
differ between humans and other species. Richard Lazarus, for example,
proposes that pride, shame and gratitude might be uniquely human emotions.
[…]
The Emotional Present
I admit that I’ve passed the emotional consciousness buck. I’ve
redefined the problem of emotional feelings as the problem of how emotional
information comes to be represented in working memory. This won’t
make you happy if you want to know exactly what a feeling is or if you
want to know how something as intangible as a feeling could be part of
something so tangible as a brain. It won’t, in other words, solve
the mind-body problem. However, as important as solving the mind-body
problem would be, it’s not the only problem worth solving. And figuring
out the mindbody problem wouldn’t tell us what’s unique about
those states of mind we call emotions, nor would it explain why different
emotions feel the way they do. Neither would it tell us what goes wrong
in emotional disorders or suggest ways of treating or curing them. In
order to understand what an emotion is and how particular emotional feelings
come about we’ve got to understand the way the specialised emotion
systems operate and determine how the activity of these gets represented
in working memory. Some might say I’m taking a big chance. I resting
our understanding of our feelings, our most private and intimate states
of mind, on the possibility that working memory is the key to consciousness.
But really what I’m doing is using working memory as an ‘in
principle’ way of explaining feelings. I’m saying that feelings
come about when the activity of specialised emotion systems gets represented
in the system that gives rise to consciousness, and I’m using working
memory as a fairly widely accepted version of how the latter might come
about.
We’ve gone into great detail as to how one specialised emotion system,
the defense system, works. So let’s now see how the activity of
this system might come to be represented in working memory and thereby
give rise to the feeling we know as fear.
From Conscious Appraisals to Emotions: You encounter a rabbit
while walking along a path in the woods. Light reflected from the rabbit
is picked up by your eyes. The signals are then transmitted through the
visual system to your visual thalamus, and then to your visual cortex,
where a sensory representation of the rabbit is created and held in a
short-term visual object buffer. Connections from the visual cortex to
the cortical long-term memory networks activate relevant memories (both
facts about rabbits stored in memory as well as memories about past experiences
you may have had with rabbits). By way of connections between the long-term
memory networks and the working memory system, activated long-term memories
are inte-grated with the sensory representation of the stimulus in working
memory, allowing you to be consciously aware that the object you are looking
at is a rabbit.
A few strides later down the path, there is a snake coiled up next to
a log. Your eyes also pick up on this stimulus. Conscious representations
are created in the same way as For the rabbit – by the integration
in working memory of short-term visual representations with information
from long-term memory. However, in the case of the snake, in addition
to being aware of the kind of animal you are looking at, long-term memory
also informs you that this kind of animal can be dangerous and that you
might be in danger. According to cognitive appraisal theories, the processes
described so far would constitute your assessment of the situation and
should be enough to account for the ‘fear’ that you are feeling
as a result of encountering the snake. The difference between the working
memory representation of the rabbit and the snake is that the latter includes
information about the snake being dangerous. But these cognitive representations
and appraisals in working memory are not enough to turn the experience
into a full blown emotional experience. Davey Crockett, you may remember,
said his love for his wife was so hot that it mighty near burst his boilers.
There is nothing equivalent to boiler bursting going on here.
Something else is needed to turn cognitive appraisals into emotions, to
turn experiences into emotional experiences. That something, of course,
is the activation of the system built by evolution to deal with dangers.
That system, as we’ve seen, crucially involves the amygdala.
Many but not all people who encounter a snake in a situation such as the
one described will have a full blown emotional reaction that includes
bodily responses and emotional feelings. This will only occur if the visual
representation of the snake triggers the amygdala. A whole host of output
pathways will then be activated. Activation of these outputs is what makes
the encounter with the snake an emotional experience, and the absence
of activation is what prevents the encounter with the rabbit from being
one.
What is it about the activation of amygdala outputs that converts an experience
into an emotional experience? To understand this we need to consider some
of the various consequences of turning on amygdala outputs. These outputs
provide the basic ingredients which, when mixed together in working memory
with short-term sensory representations and the long-term memories activated
by these sensory representations, create an emotional experience.
Ingredient 1: Direct Amygdala Influences on the Cortex: The
amygdala has projections to many cortical areas. In fact, the projections
of the amygdala to the cortex are considerably greater than the projections
from the cortex to the amygdala. In addition to projecting back to cortical
sensory areas that it receives inputs from, the amygdala also projects
to some sensory processing areas that it does not receive from. For example,
in order for a visual stimulus to reach the amygdala by way of the cortex,
the stimulus has to go through the primary cortex, to a secondary region,
and then to a third cortical area in the temporal lobe (this is the same
area that does the short-term buffering of visual object information).
This third area then projects to the amygdala. The amygdala projects back
to this area, but also to the other two earlier visual processing regions.
As a result, once the amygdala is activated, it is able to influence the
cortical areas that are processing the stimuli that are activating the
it. This might be very important in directing attention to emotionally
relevant stimuli by keeping the shortterm object buffer focused on the
stimuli that the amygdala is assigning significance to. The amygdala also
has an impressive set of connections with long-term memory networks involving
the hippocampal system and areas of cortex that interact with the hippocampus
in long-lasting information storage. These pathways may contribute to
the activation of long-term memories relevant to the emotional implications
of immediately present stimuli. Although the amygdala has relatively meager
connections with the lateral prefrontal cortex, it sends rather strong
connections to the anterior cingulate cortex, one of the other partners
in the frontal lobe working memory executive circuitry. It also sends
connections to the orbital cortex, another player in working memory that
may be especially involved in working memories about rewards and punishments
(see above). By way of these connections with specialised short-term buffers,
long-term memory networks, and the networks of frontal lobe, the amygdala
can influence the information content of working memory. There is obviously
a good deal of redundancy built into this system, making it possible for
the conscious awareness of amygdala activity to come about in several
ways.
In sum, connections from the amygdala to the cortex allow the defense
networks of the amygdala to influence attention, perception, and memory
in situations where we are facing danger. At the same time, though, these
kinds of connections would seem to be inadequate in completely explaining
why a perception, memory, or thought about an emotional event should ‘feel’
different from one about a non-emotional event. They provide working memory
with information about whether something good or bad is present, but are
insufficient for producing the feelings that come from the awareness that
something good or bad is present. For this we need other connections as
well.
Ingredient 2: Amygdala Triggered Arousal: In addition to these
direct influences of the amygdala on the cortex, there are a number of
indirect channels through which the effects of amygdala activation can
impact on cortical processing. An extremely important set of such connections
involve the arousal systems of the brain.
It has long been believed that the difference between being awake and
alert, on the one hand, and drousy or asleep on the other is related to
the arousal level of the cortex. When you are alert and paying attention
to something important, your cortex is aroused. When you are drousey and
not focusing on anything, the cortex is in the un-aroused state. During
sleep, the cortex is in the unaroused state, except during dream sleep
when it is highly aroused. In dream sleep, in fact, the cortex is in a
state of arousal that is very similar to the alert waking state, except
that it has no access to external stimuli and only processes internal
events.
Cortical arousal can be easily detected by putting electrodes on the scalp
of a huamn. These electrodes pick up the electrical activity of cortical
cells through the skull. This electroencephalogram or EEG is slow and
rhythmic when the cortex is not aroused and fast and out of sync (desynchronised)
during arousal.
When arousal occurs, cells in the cortex, and in the thalamic regions
that supply the cortex with its major inputs, become more sensitive. They
go from a state in which they tend to fire action potentials at a very
slow rate and more or less in synchrony to a state in which they are generally
out of sync but with some cells being driven especially strongly by incoming
stimuli.
While much of cortex is potentially hyper-sensitive to inputs during arousal,
the systems that are processing information are able to make the most
use of this effect. For example, if arousal is triggered by the sight
of a snake, the neurons that are actively involved in processing the snake,
retrieving long-term memories about snakes, and creating working memory
representations of the snake, are going to be especially affected. Other
neurons are inactive at this point and don’t reap the benefits.
In this way, a very specific information processing result is achieved
by a very nonspecific mechanism. This is a wonderful evolutionary trick.
A number of different systems appear to contribute to arousal. Three of
these are located in regions of the brainstem. Each has a specific chemical
identity, which means the cells in each contain different neurotransmitters
that are released by their axon terminals when the cells are activated.
One group makes acetylcholine (ACh), another noradrenaline, and another
serotonin. A fourth group, also containing ACh, is located in the forebrain,
near the amygdala. The axons of each these cells groups terminate in widespread
areas of the forebrain. In the presence of novel or otherwise significant
stimuli the axon terminals release their neruotransmitters and ‘arouse’
cortical cells, making them especially receptive to incoming signals.
Arousal is important in all mental functions. It contributes significantly
to attention, perception, memory, emotion, and problem solving. Without
arousal, we fail to notice what is going on—we don’t attend
to the details. But too much arousal is not good either. You need to have
just the right level of activation to perform optimally. If you are overaroused
you become tense and anxious and unproductive.
This is sometimes called the Yerkes-Dodson Law.
Emotional reactions are typically accompanied by intense cortical arousal.
Certain emotion theories around mid century proposed that emotions represent
one end of an arousal continuum that spans from being completely unconscious
(in a coma), to asleep, to awake but drousy, to alert, to emotionally
aroused. This high level of arousal is, in part, the explanation for why
it is hard to concentrate on other things and work efficiently when you
are in an emotional state. Arousal helps lock you into the emotional state.
This can be very useful (you don’t want to get distracted when you
are in danger), but can also be an annoyance (once the fear system is
turned on, its hard to turn it off – this is the nature of anxiety).
Although each of the arousal systems probably contributes to arousal in
the presence of stimuli that are dangerous or that warn of danger, it
appears that interactions between the amygdala and the nearby ACh containing
system in the forebrain are particularly important. This ACh containing
system is called the nucleus basalis. Damage to the amygdala or to the
nucleus basalis prevents stimuli that warn of danger, like conditioned
fear stimuli, from eliciting arousal. Moreover, stimulation of the amygdala
or the nucleus basalis elicits cortical arousal artificially. And administration
of drugs that block the actions of ACh in the cortex prevents these effects
on arousal of conditioned stimuli, amygdala stimulation or nuclues basalis
stimulation from occurring. Together, these and other findings suggest
that when the amygdala detects danger it activates the nucleus basalis
which then releases ACh throughout the cortex. The amygdala also interacts
with the other arousal systems located in the brainstem and the overall
effect of amygdala activation on arousal certainly involves these as well.
Although there are a number of different ways that the nucleus basalis
cells can be turned on, the way they are turned on by a dangerous stimulus
is through the activity of the amygdala. Other kinds of emotional networks
most likely have their own ways of interacting with the arousal systems
and altering cortical processing. Arousal occurs to any novel stimulus
that we encounter and not just to emotional stimuli. The difference is
that a novel but insignificant stimulus will elicit a temporary state
of arousal that dissipates almost immediately but arousal is prolonged
in the presence of emotional stimuli. If you are face to face with a predator
it is crucial that you not lose interest in what is going on or be distracted
by some other event. While this seems so obvious as to be silly, it is
only so because the brain does it so effortlessly.
Why is arousal perpetuated to emotional but not to other stimuli? Again,
the answer probably has to do with the involvement of the amygdala. The
arousal elicited by a novel stimulus does not require the amygdala. Instead,
it is mediated by direct inputs from sensory systems to arousal networks.
These kinds of arousal effects quickly habituate. If the stimulus is meaningful,
say dangerous, then the amygdala is brought into the act and it also activates
arousal systems. This adds impetus to keep arousal going. The continued
presence of the stimulus and its continued interpretation by the amygdala
as dangerous continues to drive arousal systems, and these systems, in
turn, keep cortical networks that are processing the stimulus in a state
of hypersensitivity. The amygdala, it should be noted, is also the recipient
of arousal system axons, so that amygdala activation of arousal systems
also helps keep the amygdala aroused. These are self-perpetuating, viscous
cycles of emotional reactivity. Arousal locks you into whatever emotional
state you are in when arousal occurs, unless something else occurs that
is significant enough and arousing enough to shit the focus of arousal.
The information content provided by arousal systems is weak. The cortex
is unable to discern that danger (as opposed to some other emotional condition)
exists form the pattern of neural messages it receives from arousal systems.
Arousal systems simply say that something important is going on. The combination
of non-specific cortical arousal and specific information provided by
direct projections from the amygdala to the cortex allows the establishment
of a working memory that says that something important is going on and
that it involves the fear system of the brain. These representations converge
in working memory with the representations from specialised short-term
memory buffers and with representations from long-term memory triggered
by current stimuli and by amygdala processing. The continued driving of
the amygdala by the dangerous stimulus keeps the arousal systems active,
which keeps the amygdala and cortical networks actively engaged in the
situation as well. Cognitive inference and decision making processes controlled
by the working memory executive become actively focused on the emotionally
arousing situation, trying to figure out what is going on and what should
be done about it. All other inputs that are vying for the attention of
working memory are blocked out.
We now have many of the basic ingredients for a complete emotional experience.
But one more is needed. |
